Double transition shift control in an automatic powershifting transmission

ABSTRACT

A system and method for controlling double transition shifts in an automatic transmission having multiple gear sections. During a double transition shift, the system performs simultaneous closed loop control of the primary oncoming clutch in the primary gear section and the secondary off-going clutch of the secondary gear section. Before the input shaft of the secondary gear section is fully pulled down or the secondary off-going clutch becomes overheated, the system switches closed loop control of the input shaft to the secondary on-coming clutch of the secondary gear section. The system utilizes model-based calculations to determine the initial clutch pressure settings when a clutch enters closed loop control.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/412,961 filed Nov. 12, 2010, which is herebyincorporated by reference.

BACKGROUND

The present invention generally relates to a vehicle transmissioncontrol system and, more particularly, to a system and method forcontrolling double transition shifts in transmissions which utilizemultiple gearing sections.

Motor vehicles require a transmission between the vehicle engine ormotor and the output drive elements in order to optimize efficiency andprovide the desired torque and acceleration characteristics undervarying driving conditions while maintaining the engine or motor withinoperational speeds. A typical transmission includes a number ofindividual gear elements which may be selectively engaged using acorresponding set of individual clutches. The combination of activatedclutches determines the overall speed ratio between the input and outputshafts of the transmission. In a simple transmission, a shift from acurrent speed ratio to a new speed ratio involves disengaging a firstclutch, known as the off-going clutch, and engaging a second clutch,known as the on-coming clutch. In certain applications, however, thetransmission may comprise multiple gearing sections with an intermediateshaft therebetween in order to optimize manufacturing costs, size, orother operational parameters.

The use of multiple gearing sections may result in at least one instancewhere multiple clutches in the transmission are being engaged ordisengaged at the same time in order to achieve a desired change in theoverall speed ratio of the transmission. For example, in a ten-speedtransmission comprising a five-speed range pack followed by a two-speedsplitter unit, the shift from fifth to sixth gear involves thecoordination of four clutches: the off-going and on-coming clutches inthe range pack, as well as the off-going and on-coming clutches in thesplitter unit. These shifts, commonly referred to as double transitionshifts, are more difficult to control due to the complex interactionsbetween the simultaneous shifts in the range pack and splitter unit.Furthermore, a double transition shift often requires that onetransmission section (e.g., the range pack) be shifted from its highestgear ratio to its lowest gear ratio, which can result in excess heatbuildup in the clutch elements. One known method for dealing with theproblem is to simply speed up the rate of the shift, thereby reducingthe time available for heat to build up in the clutches.

However, many transmission control systems utilize what is known as“power on shifting” where there is very little, if any, decrease indelivered output torque during a transmission shift and the shifts arecompleted in a shorter amount of time. This increases the efficiency andresponsiveness of the transmission, but also makes control of thevarious clutches and other transmission elements more difficult,particularly in the case of double transition shifts. Systems andmethods are therefore needed which improve shift quality and reducestrain on the transmission elements during double transitions shifts.

SUMMARY

According to one aspect of the present disclosure, a transmissioncontrol system is presented which utilizes at least three speed sensorsin order to optimize the control of individual clutches during doubletransition power-on shifts while still achieving a desired accelerationprofile. The speed sensors may be located on the transmission inputshaft, on an intermediate shaft between the transmission gear sections,and on the output shaft of the transmission. The transmission controlsystem may further utilize simultaneous closed loop control for both ofthe shifts involved in a double transition shift.

According to another aspect of the disclosure, the transmission controlsystem utilizes closed loop control of the intermediate shaft speed byapplying the proper amount of pressure to the primary on-coming clutchin a primary section of the transmission to ensure that the primaryon-coming clutch is fully locked up (no longer slipping) before thesecondary off-going clutch in a secondary section of the transmissionbecomes overheated. Once the primary on-coming clutch is locked up, thesystem switches closed loop control of the input shaft speed from thesecondary off-going clutch to the secondary on-coming clutch in thesecondary transmission section. In addition to real-time closed loopcontrol, the system may utilize model-based calculations to determinethe initial clutch pressures or torques necessary to achieve lockup ofthe intermediate shaft prior to the secondary off-going clutch reachingits thermal limits. This allows the transmission clutch elements to bemanufactured to lower thermal and performance standards while at thesame time, allowing the optimization of shifts during double transitionevents.

According to another aspect of the disclosure, a method for controllinga double transition upshift in an automatic transmission of a vehiclepowertrain is presented. Closed loop control of an intermediate shaftspeed is performed using a primary on-coming clutch in a primary gearsection of the automatic transmission to achieve pull-down of theintermediate shaft. The primary gear section is connected to an outputshaft and the intermediate shaft. The intermediate shaft is connectedbetween the primary gear section and a secondary gear section of theautomatic transmission. While the intermediate shaft is being pulleddown, closed loop control of an input shaft speed is performed using asecondary off-going clutch in the secondary gear section to achievepartial pull-down of the input shaft. The input shaft is connectedbetween the secondary gear section and a power generation unit of thevehicle. The secondary off-going clutch is released and closed loopcontrol of the input shaft speed is performed using a secondaryon-coming clutch in the secondary gear section to complete the pull-downof the input shaft. The secondary off-going clutch may be exhaustedbefore the secondary off-going clutch reaches a thermal capacitythreshold. Pull-down of the intermediate shaft is preferably completedbefore the secondary off-going clutch is exhausted. Initial closed-loopcontrol setpoints for the clutches may be based on a model representingthe estimated inertias within the transmission.

According to another aspect of the disclosure, a method for controllinga double transition downshift in an automatic transmission of a vehiclepowertrain is presented. Closed loop control of an intermediate shaftspeed is performed using a primary on-coming clutch in a primary gearsection of the automatic transmission to achieve pull-up of theintermediate shaft. The primary gear section is connected to an outputshaft and the intermediate shaft. The intermediate shaft is connectedbetween the primary gear section and a secondary gear section of theautomatic transmission. While the intermediate shaft is being pulled up,closed loop control of an input shaft speed is performed using asecondary off-going clutch in the secondary gear section to achievepartial pull-up of the input shaft. The input shaft is connected betweenthe secondary gear section and a power generation unit of the vehicle.The secondary off-going clutch is released and closed loop control ofthe input shaft speed is performed using a secondary on-coming clutch inthe secondary gear section to complete the pull-up of the input shaft.The secondary off-going clutch may be exhausted before the secondaryoff-going clutch reaches a thermal capacity threshold. Pull-up of theintermediate shaft is preferably completed before the secondaryoff-going clutch is exhausted. Initial closed-loop control setpoints forthe clutches may be based on a model representing the estimated inertiaswithin the transmission.

According to another aspect of the disclosure, a system for controllinga double transition upshift in an automatic transmission of a vehiclepowertrain is presented, comprising a primary gear section of theautomatic transmission, the primary gear section connected to an outputshaft, a secondary gear section of the automatic transmission, and anintermediate shaft connected between the primary gear section andsecondary gear section. An input shaft is connected between thesecondary gear section and a power generation unit of the vehicle. Atorque converter may be connected between the input shaft and the powergeneration unit. A processor-based controller is in operativecommunication with the primary and secondary gear sections. Thecontroller is configured to perform closed loop control of theintermediate shaft speed during the double transition upshift using aprimary on-coming clutch in the primary gear section to achievepull-down of the intermediate shaft. The controller is furtherconfigured to perform closed loop control of the input shaft speed usinga secondary off-going clutch in the secondary gear section to achievepartial pull-down of the input while the intermediate shaft is beingpulled down. The controller is further configured to release thesecondary off-going clutch and perform closed loop control of the inputshaft speed using a secondary on-coming clutch in the secondary gearsection to complete the pull-down of the input shaft. The controller mayalso be configured to exhaust the secondary off-going clutch before thesecondary off-going clutch reaches a thermal capacity threshold. Thecontroller may further be configured to substantially complete pull-downof the intermediate shaft before the secondary off-going clutch isexhausted. The controller may also be configured to determine at leastone initial clutch setpoint for closed loop control based on a modelrepresenting a plurality of estimated inertias within the transmission.

According to another aspect of the disclosure, a system for controllinga double transition downshift in an automatic transmission of a vehiclepowertrain is presented, comprising a primary gear section of theautomatic transmission, the primary gear section connected to an outputshaft, a secondary gear section of the automatic transmission, and anintermediate shaft connected between the primary gear section andsecondary gear section. An input shaft is connected between thesecondary gear section and a power generation unit of the vehicle. Atorque converter may be connected between the input shaft and the powergeneration unit. A processor-based controller is in operativecommunication with the primary and secondary gear sections. Thecontroller is configured to perform closed loop control of theintermediate shaft speed during the double transition upshift using aprimary on-coming clutch in the primary gear section to achieve pull-upof the intermediate shaft. The controller is further configured toperform closed loop control of the input shaft speed using a secondaryoff-going clutch in the secondary gear section to achieve partialpull-up of the input shaft while the intermediate shaft is being pulledup. The controller is further configured to release the secondaryoff-going clutch and perform closed loop control of the input shaftspeed using a secondary on-coming clutch in the secondary gear sectionto complete the pull-up of the input shaft. The controller may also beconfigured to exhaust the secondary off-going clutch before thesecondary off-going clutch reaches a thermal capacity threshold. Thecontroller may further be configured to substantially complete pull-downof the intermediate shaft before the secondary off-going clutch isexhausted. The controller may also be configured to determine at leastone initial clutch setpoint for closed loop control based on a modelrepresenting a plurality of estimated inertias within the transmission.

The above concept may be extended to transmissions having three or moregear sections. For example, transmissions having three gear sections mayrequire a triple transition shift, where all three gear sections arebeing shifted simultaneously. In such cases, additional speed sensorsmay be added to monitor the additional shafts(s) connecting thetransmission sections. Additionally, the closed loop control of theprimary, secondary, and tertiary clutches may be switched from theoff-going to the on-coming clutches in a cascaded fashion to avoidoverheating of the off-going clutches.

Further forms, objects, features, aspects, benefits, advantages, andembodiments of the present invention will become apparent from adetailed description and drawings provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of a transmission and associatedtransmission control system according to one embodiment of the presentdisclosure.

FIG. 2 is a table which lists the activated clutches for each availableforward speed ratio in an example multi-unit transmission.

FIG. 3 is a diagram showing the timing of the pressure level commands inthe primary on-coming and primary off-going clutches in the rearplanetary gearset of the transmission of FIG. 1 during a doubletransition upshift according to one embodiment of the presentdisclosure.

FIG. 4 is a diagram showing the timing of the pressure level commands inthe secondary on-coming and off-going clutches in the countershaftgearset of the transmission of FIG. 1 during a double transition upshiftaccording to one embodiment of the present disclosure.

FIG. 5 is a diagram showing the timing of the resulting pressure levelsin the primary on-coming and primary off-going clutches in the rearplanetary gearset of the transmission of FIG. 1 during a doubletransition upshift according to one embodiment of the presentdisclosure.

FIG. 6 is a diagram showing the timing of the resulting pressure levelsin the secondary on-coming and off-going clutches in the countershaftgearset of the transmission of FIG. 1 during a double transition upshiftaccording a one embodiment of the present disclosure.

FIG. 7 is a diagram showing the resulting change in input shaft speed,intermediate shaft speed, and output shaft speed with time based on thecontroller clutch pressure commands of FIGS. 3 and 4.

FIG. 8 is a diagram showing the timing of the pressure level commands inthe primary on-coming and primary off-going clutches in the rearplanetary gearset of the transmission of FIG. 1 during a doubletransition downshift according to one embodiment of the presentdisclosure.

FIG. 9 is a diagram showing the timing of the pressure level commands inthe secondary on-coming and off-going clutches in the countershaftgearset of the transmission of FIG. 1 during a double transitiondownshift according to one embodiment of the present disclosure.

FIG. 10 is a diagram showing the timing of the resulting pressure levelsin the primary on-coming and primary off-going clutches in the rearplanetary gearset of the transmission of FIG. 1 during a doubletransition downshift according to one embodiment of the presentdisclosure.

FIG. 11 is a diagram showing the timing of the resulting pressure levelsin the secondary on-coming and off-going clutches in the countershaftgearset of the transmission of FIG. 1 during a double transitiondownshift according a one embodiment of the present disclosure.

FIG. 12 is a diagram showing the resulting change in input shaft speed,intermediate shaft speed, and output shaft speed with time based on thecontroller clutch pressure commands of FIGS. 8 and 9.

DESCRIPTION OF THE SELECTED EMBODIMENTS

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings, and specific language will be used to describe the same.It will nevertheless be understood that no limitation of the scope ofthe invention is thereby intended. Any alterations and furthermodifications in the described embodiments and any further applicationsof the principles of the invention as described herein are contemplatedas would normally occur to one skilled in the art to which the inventionrelates. One embodiment of the invention is shown in great detail,although it will be apparent to those skilled in the relevant art thatsome features not relevant to the present invention may not be shown forthe sake of clarity.

FIG. 1 shows a diagrammatic view of a vehicle powertrain system 100which may be controlled using the methods of the present disclosure. Thecontrol methods described herein are applicable to any type of vehiclepowertrain requiring multiple transition shifts. It shall be understoodthat the transmission gear and control elements shown in FIG. 1 aremerely one example of a multi-unit transmission system that may becontrolled and that the principles of the present disclosure apply tothe control of other types of compound transmission units as well. Thesystem 100 illustrated in FIG. 1 is adapted for use in commercial-gradetrucks as well as other types of vehicles, but it is envisioned thatvarious aspects of the system 100 can be incorporated into otherenvironments. For example, the described methods may be used to controltransmissions which are connected to gasoline engines, electric motors,hybrid power sources, or any power device capable of powering a vehicle,pump, or generator via a transmission.

As shown, the system 100 may include a transmission 102, a powergeneration unit (such as engine 114), torque converter 112, vehicledrive elements 118, transmission control unit 120, and engine controlunit 121.

Transmission 102 includes a countershaft gearset 104 and a planetarygearset 106. The physical architecture of the illustrated transmission102 is similar to that described in U.S. Pat. Application PublicationNo. 2010/0029431 to Rodgers, published Feb. 4, 2010, which is hereinincorporated by reference in its entirety. Accordingly, the gear andcontrol elements shown in FIG. 1 have been simplified for the sake ofbrevity, it being understood that further details regarding theillustrated transmission architecture may be found in the aforementionedpublication.

The input shaft 110 is connected to and driven by the output of aturbine, shown here as a torque converter 112. The torque converterprovides a fluidic coupling between the engine 114 and the transmission102. Under certain conditions, the torque converter may also operate ina locked mode, in which the input and output sections of the converterbecome physically locked to reduce pumping losses and increaseefficiency. The countershaft gearset 104 outputs torque to the planetarygearset 106 via the intermediate shaft 108. The planetary gearset 106outputs torque to the vehicle drive elements 118 (e.g., wheels) via theoutput shaft 116.

Within the countershaft gearset 104, drive gears 130, 132, 134, 136 arecoupled to and in common rotation with the input shaft 110. Countershaftgearset 104 also includes first and second countershafts 138, 140 whichare generally parallel to input shaft 110. Range gears 142 and 144 arerotatable about and concentric with first countershaft 138, and furtherintermesh with drive gears 132 and 134 respectively. Range gears 146 and148 are rotatable about and concentric with second countershaft 140, andfurther intermesh with drive gears 130 and 136 respectively. Gears 150and 152 are in common rotation with first and second countershafts 138and 140 respectively, and further intermesh with gear 154. Gear 154 isin common rotation with intermediate shaft 108, which is concentric withand rotatable about input shaft 110. Drive gear 130 also intermesheswith reverse idler 131, which in turn intermeshes with range gear 133.Range gear 133 is concentric with and rotatable about first countershaft138. Synchronizer 135 is provided to provide selection between forwardand reverse speed ranges. When synchronizer 135 is moved to the “F”position, it engages range gear 142 to provide a forward speed ratio.When synchronizer 135 is moved to the “R” position, it engages rangegear 133 (which in turn engages reverse idler 131) to provide a reversespeed ratio.

Planetary gearset 106 includes a sun gear 155, a ring gear 156, aplurality of planetary gears 158 and a carrier 160 which is coupled forcommon rotation with output shaft 116. In addition, hubs 162 and 164 aredisposed at the front of the planetary gearset 106 and are operativelycoupled to input shaft 110 and intermediate shaft 108, respectively, asshown.

The countershaft gearset 104 and planetary gearset 106 contain aplurality of individual friction clutches C1-C7 as shown for selectivelyengaging the various gear elements within the countershaft and planetarygearsets 104, 106, thereby providing the desired input/output speedratio of the transmission 102. For example, with clutch C1 fullyengaged, range gear 146 is coupled to second countershaft 140, therebytransferring torque from the input shaft 110 to the intermediate shaft108. With clutch C7 additionally engaged, torque from the intermediateshaft 108 is transferred to ring gear 156 and ultimately to output shaft116 via planetary gears 158 and carrier gear 160.

Although the illustrated embodiment depicts a five-speed range pack(countershaft gearset 104) followed by a two-speed splitter (planetarygearset 106), other types of transmissions may be controlled using theprinciples of the present disclosure. In addition, the individualgearsets 104, 106 may comprise any type of transmission architectureknown the art including, but not limited to, countershaft gearsets,planetary gearsets, and the like.

A transmission control unit 120 is included which is in operativecommunication with various sensors in the vehicle powertrain including,but not limited to, speed sensors 122, 124, and 126. Sensor 122 isconnected to the transmission input shaft 110, sensor 124 is connectedto the intermediate shaft 108, and sensor 126 is connected to the outputshaft 126. The speed sensors 122-126 sense the angular velocity of thecorresponding shafts and provide feedback to the transmission controlunit 120 to aid in the control of the individual clutches that will bedescribed hereinbelow. The transmission control unit 120 may alsointerface with or include hydraulic connections for actuating theclutches C1-C7 using various methods known in the art. In addition, thetransmission control unit 120 may receive additional signals, such asengine output torque or engine speed, from other sensors or powertraincontrol components, including engine control unit 121.

In a typical embodiment, the transmission controller 120 and enginecontrol unit 121 each comprise a computer having a processor, memory,and input/output connections. The transmission control unit 120 may alsoinclude hydraulic switching and actuating components for routing andcontrolling the flow of hydraulic fluid to the various clutches andtransmission components. It shall be understood that additional elementsmay be included in the transmission control unit 120 and engine controlunit 121 as required by the particular application.

FIG. 2 illustrates the states of the individual clutch elements for eachof the ten forward speed ratios being provided by the transmission 102.From the first to fifth speed ratios, only one off-going and oneon-coming clutch transition is required for each shift. However, theshift between the fifth and sixth gear ranges is a double transitionshift, which involves an off-going (C5) and on-coming (C1) clutch in thecountershaft gearset 104, as well as an off-going (C6) and on-coming(C7) clutch in the planetary gearset 106. One problem with thisparticular transition is that the speed ratio of the countershaftgearset 104 must be transitioned from its lowest ratio to its highestratio in a single shift. If the off-going clutch (C5) were used as themain control element for pulling down the speed of the input shaft 110during the shift, the resulting heat strain due to the large clutch slipspeeds and input torque from power-on shifting could cause decreasedcomponent life or even catastrophic failure. This can be a particularproblem if the countershaft gearset was originally designed for use as asingle unit transmission requiring only incremental shifts.

FIGS. 3, 4, 5, 6, and 7 illustrate a method for controlling theindividual clutch pressures during a double transition upshift accordingto one embodiment of the present disclosure. Because the planetarygearset 106 is in direct communication with the output shaft 116, theclutches C6 and C7 will be respectively referred to as the primaryoff-going and primary on-coming clutches involved in the control of thedouble transition upshift. Likewise, the clutches C1 and C5 will berespectively referred to as the secondary on-coming and secondaryoff-going clutches for the double transition upshift. However, it shallbe appreciated that other types of gearing elements may be substitutedfor the planetary gearset 106 and countershaft gearset 104.

Turning to FIG. 3, at time τ₁, a shift from the fifth to sixth overallspeed ratio is initiated by the transmission control unit 120. Thetransmission control unit 120 first increases the pressure of theprimary oncoming clutch (C7) during a fill phase in order to synchronizethe primary oncoming clutch's capacity with the secondary offgoingclutch (C5) slip for simultaneous shifts (e.g., the shift of thecountershaft gearset 104). The pressure of the primary off-going clutch(C6) may also be lowered at time τ₁ to allow for smoother control andpredictable behavior when the primary off-going clutch (C6) needs to beexhausted. At approximately time τ₂, the pressure in the primaryoncoming clutch (C7) is commanded to a level which will begin to pulldown the speed of the intermediate shaft 108 at a desired rate during aninertia phase. Also at approximately time τ₂, the primary off-goingclutch (C6) is exhausted, thereby relinquishing control of theintermediate shaft 108 speed to the primary oncoming clutch (C7). Atthis point, the speed of the intermediate shaft 108 is being mostlycontrolled by the primary oncoming clutch (C7) in a closed loop controlmode which utilizes the intermediate shaft speed sensor 124 in afeedback loop.

As shown in FIG. 4, at time τ₂, the transmission control unit 120 alsolowers the pressure of the secondary off-going clutch (C5), therebyallowing the secondary off-going clutch (C5) to begin slipping and entera closed loop control mode. The input shaft speed sensor 122 providesfeedback for the control of the input shaft 110 speed. The secondaryon-coming clutch (C1) enters a fill phase at this time as well. Fromtime τ₂ to τ₃, both the primary oncoming clutch (C7) and the secondaryoff-going clutch (C5) are operating in closed loop control mode, withclutch C7 controlling the intermediate shaft 108 speed and clutch C5controlling the input shaft 110 speed.

Once the calculated slip speed of the secondary off-going clutch (C5)has exceeded a thermal capacity threshold (at time τ₃ in FIG. 7), thesecondary off-going clutch (C5) is exhausted. The pressure in theprimary oncoming clutch (C7) is preferably controlled from time τ₂ to τ₃to ensure that pull-down of the intermediate shaft 108 is also completedby time τ_(3,) thereby preventing negative output torque on the outputshaft 116. Since no clutch is acting against the primary oncoming clutch(C7) locking the intermediate shaft 108, the primary oncoming clutch(C7) locks up at time τ₃. The secondary oncoming clutch (C1) is then setto a pressure level adequate for maintaining the continued pull-down andcontrol of the input shaft 110. The transmission controller 120maintains control of the input shaft 110 speed via the secondary comingclutch (C1) in a closed loop control mode (using input shaft speedsensor 122 as the feedback component) until time τ₄ when pull down ofthe input shaft 110 is complete. By transitioning control of the inputshaft 110 speed from the secondary off-going clutch (C5) to thesecondary oncoming clutch (C1) before pull-down of the input shaft 110is complete, the secondary off-going clutch (C5) is prevented fromoverheating or experiencing excessive wear. Additionally, the secondaryoncoming clutch C1 has limited thermal impact due to low slip during itscontinued pull down of the input shaft 110. FIGS. 5 and 6 illustrateexample corresponding clutch pressures which result from the clutchpressure command sequences of FIGS. 3 and 4.

FIGS. 8, 9, 10, 11, and 12 illustrate a method for controlling theindividual clutch pressures during a double transition closed throttledownshift according to a further embodiment of the present disclosure.For the double transition downshift, clutch C7 will operate as theprimary off-going clutch and clutch C6 will operate as the primaryon-coming clutch. Likewise, clutch C1 will operate as the secondaryoff-going clutch and clutch C5 will operate as the secondary on-comingclutch.

As shown in FIG. 8, the primary on-coming clutch (C6) begins a fillphase at time τ₁ when the double transition downshift is initiated. Attime τ₂, the primary off-going clutch (C7) is exhausted and the primaryon-coming clutch (C6) takes over control of the intermediate shaft 108speed, using the intermediate shaft speed sensor 124 as a feedbackelement. As shown in FIG. 9, at time τ₂, the secondary on-coming clutch(C5) enters a fill phase and the secondary off-going clutch (C1) entersa closed-loop control mode in relation to input shaft 110, using speedsensor 122 as feedback for the control loop. From time τ₂ to τ₃, thecontrol unit 120 performs simultaneous closed-loop control of theintermediate shaft 108 speed and input shaft 110 speed using the primaryoncoming (C6) and secondary off-going (C1) clutches respectively. Oncethe speed of the intermediate shaft 108 has been pulled-up or increasedto the desired speed at time τ₃ according to the correspondingacceleration profile, the secondary off-going clutch (C1) is exhausted.The primary oncoming clutch (C6) and secondary oncoming clutch (C5) arethen fully activated, thereby completing the double transition downshiftfrom sixth to fifth gear.

In the illustrated embodiment, the secondary off-going clutch (C1) isused to control the speed of the input shaft 110 for the duration of thedouble transition downshift, although it shall be understood that thesecondary oncoming clutch (C5) may be used to take over control of theinput shaft 110 speed at a predetermined time or pressure level in orderto prevent secondary off-going clutch (C1) from overheating as describedabove in relation to the double transition upshift. Although use of thesecondary oncoming clutch (C5) to control input shaft 110 speed in thisway may be beneficial in certain conditions where large negative inputtorques generate excessive clutch heat, such as engine braking, theremay be other reasons to restrict such use, including torque securityconcerns. FIGS. 10 and 11 illustrate example corresponding clutchpressures which result from the clutch pressure command sequences ofFIGS. 8 and 9.

In order to calculate the active clutch torques (which are functionallyrelated to clutch pressures when the clutch is slipping) required toachieve the desired acceleration profiles, a model of the transmissionis developed based on the estimated inertias of the individual gearcomponents of the transmission 102. The calculated values are used todetermine the initial clutch pressure values at the beginning of theclosed loop control phase for each clutch. The following equationsrepresent the torque relationships corresponding to the individualinertial masses within the transmission 102. For each inertial mass, thesum of the torques acting on the mass is presumed to equal zero.

α₁ I ₁−τ_(G1) G ₁+τ_(C3)=0   (1)

α₂ I ₂−τ_(C3)−τ_(C1)+τ_(G7) G ₇=0   (2)

α₃ I ₃−τ_(G4) G ₄+τ_(C1)=0   (3)

α₄ I ₄−τ_(G8)−τ_(C4)−τ_(G7)+τ_(C7)+τ_(Cc) R _(s)=0   (4)

α₅ I ₅−τ_(C7)+τ_(C6) −R _(R)τ_(Cc)=0   (5)

α₆ I ₆−τ_(Cc)+τ_(O)=0   (6)

α₇ I ₇+τ_(G1)+τ_(G2)+τ_(G3)+τ_(G4)+τ_(G5)−τ_(I)+τ_(C4)=0   (7)

α₈ I ₈−τ_(G2) G ₂+τ_(C5)=0   (8)

α₉ I ₉+τ_(G8) G ₈−τ_(C2)−τ_(C5)=0   (9)

α₁₀ I ₁₀−τ_(SF)−τ_(SR)+τ_(C2)=0   (10)

α₁₁ I ₁₁−τ_(G3) G ₃+τ_(SF)=0   (11)

α₁₂ I ₁₂−τ_(G6) G ₆+τ_(SR)=0   (12)

α₁₃ I ₁₃−τ_(G5) G ₅+τ_(G6)=0   (13)

where:

-   -   α₁=angular acceleration of range gear 148    -   α₂=angular acceleration of countershaft 140    -   α₃=angular acceleration of range gear 146    -   α₄=angular acceleration of intermediate shaft 108    -   α₅=angular acceleration of ring gear 146    -   α₆=angular acceleration of output shaft 116    -   α₇=angular acceleration of input shaft 110    -   α₈=angular acceleration of range gear 144    -   α₉=angular acceleration of countershaft 138    -   α₁₁=angular acceleration of synchronizer 135    -   α₁₁=angular acceleration of range gear 142    -   α₁₂=angular acceleration of reverse gear 133    -   α₁₃=angular acceleration of reverse idler 131    -   I_(n)=inertia of element associated with α_(n), where n=1 to 13    -   τ_(C1) through τ_(C7)=applied torques of clutches C1 through C7,        respectively    -   G₁=gear ratio between gears 136 and 148    -   G₂=gear ratio between gears 134 and 144    -   G₃=gear ratio between gears 132 and 142    -   G₄=gear ratio between gears 130 and 146    -   G₅=gear ratio between gears 130 and 131    -   G₆=gear ratio between gears 131 and 133    -   G₇=gear ratio between gears 152 and 154    -   G₈=gear ratio between gears 150 and 154    -   τ_(Gn)=gear torques applied between gears associated with G_(n),        where n=1 to 8    -   τ_(SF)=torque being applied by synchronizer 135 in forward mode    -   τ_(SR)=torque being applied by synchronizer 135 in reverse mode    -   τ_(I)=input torque applied to input shaft 110    -   τ_(O)=output torque applied to output shaft 116    -   R_(S)=gear ratio corresponding to sun gear 155    -   R_(R)=gear ratio corresponding to ring gear 158    -   τ_(Cc)=torque being applied by carrier 150 and planetary gear        158

In the above representations, each inertial element, such as input shaft110, includes the inertias of all fixedly attached rotating elements. Inthe case of input shaft 110, this would include the drive gears 130,132, 134, 136, and hub 162. τ_(C1)-τ_(C7) represent the torques of theclutches C1-C7.

In addition, the following shaft angular acceleration relationships maybe developed based on the transmission 102.

α₇G₁=α₁   (14)

α₄G₇=α₂   (15)

α₇G₄=α₃   (16)

α₇G₂=α₈   (17)

α₄G₈=α₉   (18)

α₇G₃=α₁₁   (19)

α₁₃G₆=α₁₂   (20)

α₇G₅=α₁₃   (21)

α₆ =R _(S)α4+R _(R)α₅   (22)

An additional equation may be added to the 22 system equations above tospecify direction, based on the position of the synchronizer 135. Ifsynchronizer 135 is in the forward position, equation (23) below holdstrue, and τ_(SR) will equal zero.

α₁₀−α₁₁=0   (23)

Likewise, if synchronizer 135 is in the reverse position, equation (24)below holds true, and τ_(SF) will equal zero.

α₁₀−α₁₂=0   (24)

It may also be observed that the following conditions are true when theindividual clutches C1-C7 are locked.

C1 locked: α₂=α₃   (25)

C2 locked: α₉=α₁₀   (26)

C3 locked: α₁=α₂  (27)

C4 locked: α₄=α₇   (28)

C5 locked: α₈=α₉   (29)

C6 locked: α₅=0   (30)

C7 locked: α₄=α₅   (31)

In the above equations, there are 33 variables: 13 accelerations(α₁-α₁₃), 9 gear torques (τ_(G1)-τ_(G8) and τ_(Cc)), 2 synchronizertorques (τ_(SF) and τ_(SR)), 7 clutch torques (τ_(C1)-τ_(C7)), inputtorque (τ_(I)), and output torque (τ_(O)). There are 22 systemequations: 13 torque balancing equations (equations (1)-(13)), and 9speed balancing equations (equations (14)-(22)). The additional equationfor speed direction (either (23) or (24), depending on direction),yields 23 total system equations.

These equations result in 23 dependent variables (α₁-α₁₃, τ_(G1)-τ_(G8),τ_(C) & τ_(SF)/τ_(SR)) and 10 independent variables (τ_(SR)/τ_(SF),τ_(C1)-τ_(C7), τ_(I), and τ_(O)). Each dependent variable can be solvedas a function of the independent variables, resulting in a set of 23solved system equations as a function of the 10 independent variables.Using the solved system equations that calculate the output, input andcountershaft accelerations (α₄, α₇ and α₉ respectively), the activeclutch torques can be solved. The inactive clutches (and the previouslymentioned synchronizer torque) are set to zero torque (five inactiveclutches and the inactive synchronizer during the inertia phase of theshift) and output torque can be estimated, leaving only threeindependent variables (two active clutches and input torque) to controlthe three dependent accelerations.

For example, in the double transition upshift illustrated in FIGS. 3-7,the active clutches are C7 (primary oncoming), C5 (secondary offgoing),and/or C1 (secondary oncoming). The remaining clutches C2-C4 and C6 canbe assumed to have desired torques of zero during the inertia phase ofthe shift. In addition, the variables τ_(O) and α₆, which are not beingcontrolled, are assumed constant based on shift initiation measurements.This results in the following equations for τ_(C5), τ_(C7), and τ_(I),where K_(x,y) are constants (x=1-3, y=1-3)

τ_(C5) =K _(1,1)*(α_(7desired))+K _(1,2)*(α_(4desired))+K_(1,3)*(α_(6desired))   (30)

τ_(C7) =K _(2,1)*(α_(7desired))+K _(2,2)*(α_(4desired))+K_(2,3)*(α_(6desired))   (31)

τ_(I) =K _(3,1)*(α_(7desired))+K _(3,2)*(α_(4desired))+K_(3,3)*(α_(6desired))   (32)

The above equations may be used to set the initial active clutch torquesand associated pressures for C5, C7, and τ_(I) based on the desiredshaft acceleration profiles for the 5-6 double transition upshift.

In situations where it is not possible to control input torque (τ_(I)),such as with engines which do not implement Shift Energy Management(SEM), input torque can be used in place of output torque accelerationto calculate τ_(C5) and τ_(C7) as shown in the following equations, witha new set of constants K′.

τ_(C5) =K′ _(1,1)*(α_(7desired))+K′ _(1,2)*(α_(4desired))+K′_(1,3)*(τ_(I))   (33)

Υ_(C7) =K′ ^(2,1)*(α_(7desired))+K′ _(2,2)*(α_(4desired))+K′_(2,3)*(τ_(I))   (34)

The closed loop control of the active clutches within the transmission102 may be achieved using any control method known in the art. In oneembodiment, a simple proportional control may be used which evaluatesthe error between the desired shaft speed (e.g., input shaft 110,intermediate shaft 108, or output shaft 116) and actual shaft speedmeasured by the corresponding speed (sensor 122, 124, or 126) andapplies a gain factor (G_(x,y), x=1-3, y=1-3) in real time to determinethe revised pressure command for the clutch. For example, the equationsbelow illustrate the revised torque values for τ_(C5), τ_(C7) and τ_(I)once the closed loop control values are accounted for.

τ_(C5) =K _(1,1)*(α_(7desired))+G _(1,1)*(α_(7error))+K_(1,2)*(α_(4desired))+G _(1,2)*(α_(4error))+K _(1,3)*(α_(6desired))+G_(1,3)*(α_(6error))   (35)

τ_(C7) =K _(2,1)*(α_(7desired))+G _(2,1)*(α_(7error))+K_(2,2)*(α_(4 desired))+G _(2,2)*(a_(4error))+K _(2,3)*(α_(6 desired))+G_(2,3)*(α_(6error))   (36)

τ_(I) =K _(3,1)*(α_(7desired))+G _(3,1)*(α_(7error))+K_(3,2)*(α_(4 desired))+G _(3,2)*(α_(4error))+K _(3,3)*(α_(6 desired))+G_(3,3)*(α_(6error))   (37)

In other embodiments, proportional integral derivative control may beutilized to optimize the control. The type of closed loop control usedmay be selected based on a variety of factors, including availableprocessing power and transmission mechanical response factors.

Once the secondary off-going clutch (C5) has reached its thermalcapacity and is exhausted (at time τ₃), a different set of constants K″will be used to determine new initial values for the active clutchesbased on the equations below, with C1 being used to maintain control ofthe input shaft 110 speed instead of C5.

τ_(C1) =K″ _(1,1)*(α_(7desired))+K″ _(1,2)*(α_(4desired))+K″_(1,3)*(α_(6desired))   (38)

τ_(C7) =K″ _(2,1)*(α_(7desired))+K″ _(2,2)*(α_(4desired))+K″_(2,3)*(α_(6desired))   (39)

τ_(I) =K″ _(3,1)*(α_(7desired))+K″ _(3,2)*(α_(4desired))+K″_(3,3)*(α_(6desired))   (40)

Again, once the initial active clutch values are set using equations(38)-(40), the system will again enter closed loop control. Theequations (41)-(43) below represent revised torque values for τ_(C1),τ_(C7) and τ_(I) once the closed loop control values are compensatedfor.

τ_(C1) =K″ _(1,1)*(α_(7desired))+G _(1,1)*(α_(7error))+K″_(1,2)*(α_(4desired))+G _(1,2)*(α_(4error))+K″ _(1,3)*(α_(6desired))+G_(1,3)*(α_(6error))   (41)

τ_(C7) =K″ _(2,1)*(α_(7desired))+G _(2,1)*(α_(7error))+K″_(2,2)*(α_(4desired))+G _(2,2)*(α_(4error))+K″ _(2,3)*(α_(6desired))+G_(2,3)*(α_(6error))   (42)

τ_(I) =K″ _(3,1)*(α_(7desired))+G _(3,1)*(α_(7error))+K″_(3,2)*(α_(4desired))+G _(3,2)*(α_(4error))+K″ _(3,3)*(α_(6desired))+G_(3,3)*(α_(6error))   (43)

It shall be appreciated that the above control methods may be applied totransmission architectures having more than two gear sections. Forexample, if a transmission contains three gear sections, the controlmethod described above can be extended to optimize the triple transitionshifts. In that case, the oncoming clutch of the primary gear section(which is connected to the overall output shaft) is used to control theshaft on the input side of the primary gear section. The off-goingclutch in the secondary gear section will be used to control the speedof the shaft on the input side of the secondary gear section. Once theoff-going clutch in the secondary gear section reaches thermal capacity,the oncoming clutch of the secondary gear section can take over controlof the shaft on the input side of the secondary gear section. Byextension, once the on-coming clutch in the secondary gear sectionenters lockup, control of the input shaft of the tertiary gear section(connected to the overall input shaft) can be transferred from thetertiary off-going clutch to the tertiary on-coming clutch, therebypreventing thermal overload of the tertiary off-going clutch.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges, equivalents, and modifications that come within the spirit ofthe inventions defined by following claims are desired to be protected.All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference as if each individualpublication, patent, or patent application were specifically andindividually indicated to be incorporated by reference and set forth inits entirety herein.

1. A method for controlling a double transition upshift in an automatictransmission of a vehicle powertrain, comprising: performing closed loopcontrol of an intermediate shaft speed using a primary on-coming clutchin a primary gear section of the automatic transmission to achievepull-down of the intermediate shaft, the primary gear section connectedto an output shaft and the intermediate shaft, the intermediate shaftconnected between the primary gear section and a secondary gear sectionof the automatic transmission; while the intermediate shaft is beingpulled down, performing closed loop control of an input shaft speedusing a secondary off-going clutch in the secondary gear section toachieve partial pull-down of the input shaft, the input shaft connectedbetween the secondary gear section and a power generation unit of thevehicle; and releasing the secondary off-going clutch and performingclosed loop control of the input shaft speed using a secondary on-comingclutch in the secondary gear section to complete the pull-down of theinput shaft.
 2. The method as in claim 1, wherein the secondaryoff-going clutch is exhausted before the secondary off-going clutchreaches a thermal capacity threshold.
 3. The method as in claim 1,wherein pull-down of the intermediate shaft is substantially completedbefore the secondary off-going clutch is exhausted.
 4. The method as inclaim 1, wherein control of the intermediate shaft speed is based onfeedback from an intermediate shaft speed sensor.
 5. The method as inclaim 1, wherein control of the input shaft speed is based on feedbackfrom an input shaft speed sensor.
 6. The method as in claim 1, furthercomprising: determining at least one initial clutch setpoint for closedloop control based on a model representing a plurality of estimatedinertias within the transmission.
 7. The method as in claim 6, whereinthe primary on-coming clutch is commanded to an initial primaryon-coming setpoint prior to entering closed loop control, the initialprimary on-coming setpoint determined based on the model.
 8. The methodas in claim 6, wherein the secondary off-going clutch is commanded to aninitial secondary off-going setpoint prior to entering closed loopcontrol, the initial secondary off-going setpoint determined based onthe model.
 9. The method as in claim 6, wherein the secondary on-comingclutch is commanded to an initial secondary on-coming setpoint prior toentering closed loop control, the setpoint determined based on themodel.
 10. The method as in claim 1, wherein a torque converter isconnected between the input shaft and the power generation unit.
 11. Amethod for controlling a double transition downshift in an automatictransmission of a vehicle powertrain, comprising: performing closed loopcontrol of an intermediate shaft speed using a primary on-coming clutchin a primary gear section of the automatic transmission to achievepull-up of the intermediate shaft, the primary gear section connected toan output shaft and the intermediate shaft, the intermediate shaftconnected between the primary gear section and a secondary gear sectionof the automatic transmission; while the intermediate shaft is beingpulled up, performing closed loop control of an input shaft speed usinga secondary off-going clutch in the secondary gear section to achievepartial pull-up of the input shaft, the input shaft connected betweenthe secondary gear section and a power generation unit of the vehicle;and releasing the secondary off-going clutch and performing closed loopcontrol of the input shaft speed using a secondary on-coming clutch inthe secondary gear section to complete the pull-up of the input shaft.12. The method as in claim 11, wherein the secondary off-going clutch isexhausted before the secondary off-going clutch reaches a thermalcapacity threshold.
 13. The method as in claim 11, wherein pull-down ofthe intermediate shaft is substantially completed before the secondaryoff-going clutch is exhausted.
 14. The method as in claim 11, whereincontrol of the intermediate shaft speed is based on feedback from anintermediate shaft speed sensor.
 15. The method as in claim 11, whereincontrol of the input shaft speed is based on feedback from an inputshaft speed sensor.
 16. The method as in claim 11, further comprising:determining at least one initial clutch setpoint for closed loop controlbased on a model representing a plurality of estimated inertias withinthe transmission.
 17. The method as in claim 16, wherein the primaryon-coming clutch is commanded to an initial primary on-coming setpointprior to entering closed loop control, the initial primary on-comingsetpoint determined based on the model.
 18. The method as in claim 16,wherein the secondary off-going clutch is commanded to an initialsecondary off-going setpoint prior to entering closed loop control, theinitial secondary off-going setpoint determined based on the model. 19.The method as in claim 16, wherein the secondary on-coming clutch iscommanded to an initial secondary on-coming setpoint prior to enteringclosed loop control, the setpoint determined based on the model.
 20. Themethod as in claim 11, wherein a torque converter is connected betweenthe input shaft and the power generation unit.
 21. A system forcontrolling a double transition upshift in an automatic transmission ofa vehicle powertrain, comprising: a primary gear section of theautomatic transmission, the primary gear section connected to an outputshaft; a secondary gear section of the automatic transmission; anintermediate shaft connected between the primary gear section andsecondary gear section; an input shaft connected between the secondarygear section and an a power generation unit of the vehicle; and aprocessor-based controller in operative communication with the primaryand secondary gear sections; wherein the controller is configured toperform closed loop control of the intermediate shaft speed during thedouble transition upshift using a primary on-coming clutch in theprimary gear section to achieve pull-down of the intermediate shaft;wherein the controller is further configured to perform closed loopcontrol of the input shaft speed using a secondary off-going clutch inthe secondary gear section to achieve partial pull-down of the inputwhile the intermediate shaft is being pulled down; and wherein thecontroller is further configured to release the secondary off-goingclutch and perform closed loop control of the input shaft speed using asecondary on-coming clutch in the secondary gear section to complete thepull-down of the input shaft.
 22. The system as in claim 21, wherein thecontroller is configured to exhaust the secondary off-going clutchbefore the secondary off-going clutch reaches a thermal capacitythreshold.
 23. The system as in claim 21, wherein the controller isconfigured to substantially complete pull-down of the intermediate shaftbefore the secondary off-going clutch is exhausted.
 24. The system as inclaim 21, further comprising: an intermediate shaft speed sensoroperatively connected to the intermediate shaft and in operativecommunication with the controller; wherein control of the intermediateshaft speed is based on feedback from the intermediate shaft speedsensor.
 25. The system as in claim 21, further comprising: an inputshaft speed sensor operatively connected to the input shaft and inoperative communication with the controller; wherein control of theinput shaft speed is based on feedback from the input shaft speedsensor.
 26. The system as in claim 21, wherein the controller isconfigured to determine at least one initial clutch setpoint for closedloop control based on a model representing a plurality of estimatedinertias within the transmission.
 27. The system as in claim 26, whereinthe controller is configured to command the primary on-coming clutch toan initial primary on-coming setpoint prior to entering closed loopcontrol, the initial primary on-coming setpoint determined based on themodel.
 28. The system as in claim 26, wherein the controller isconfigured to command the secondary off-going clutch to an initialsecondary off-going setpoint prior to entering closed loop control, theinitial secondary off-going setpoint determined based on the model. 29.The system as in claim 26, wherein the controller is configured tocommand the secondary on-coming clutch to an initial secondary on-comingsetpoint prior to entering closed loop control, the setpoint determinedbased on the model.
 30. The system as in claim 21, wherein a torqueconverter is connected between the input shaft and the power generationunit.
 31. A system for controlling a double transition downshift in anautomatic transmission of a vehicle powertrain, comprising: a primarygear section of the automatic transmission, the primary gear sectionconnected to an output shaft; a secondary gear section of the automatictransmission; an intermediate shaft connected between the primary gearsection and secondary gear section; an input shaft connected between thesecondary gear section and an a power generation unit of the vehicle;and a processor-based controller in operative communication with theprimary and secondary gear sections; wherein the controller isconfigured to perform closed loop control of the intermediate shaftspeed during the double transition downshift using a primary on-comingclutch in the primary gear section to achieve pull-up of theintermediate shaft; wherein the controller is further configured toperform closed loop control of the input shaft speed using a secondaryoff-going clutch in the secondary gear section to achieve partialpull-up of the input while the intermediate shaft is being pulled up;and wherein the controller is further configured to release thesecondary off-going clutch and perform closed loop control of the inputshaft speed using a secondary on-coming clutch in the secondary gearsection to complete the pull-up of the input shaft.
 32. The system as inclaim 31, wherein the controller is configured to exhaust the secondaryoff-going clutch before the secondary off-going clutch reaches a thermalcapacity threshold.
 33. The system as in claim 31, wherein thecontroller is configured to substantially complete pull-up of theintermediate shaft before the secondary off-going clutch is exhausted.34. The system as in claim 31, further comprising: an intermediate shaftspeed sensor operatively connected to the intermediate shaft and inoperative communication with the controller; wherein control of theintermediate shaft speed is based on feedback from the intermediateshaft speed sensor.
 35. The system as in claim 31, further comprising:an input shaft speed sensor operatively connected to the input shaft andin operative communication with the controller; wherein control of theinput shaft speed is based on feedback from the input shaft speedsensor.
 36. The system as in claim 31, wherein the controller isconfigured to determine at least one initial clutch setpoint for closedloop control based on a model representing a plurality of estimatedinertias within the transmission.
 37. The system as in claim 36, whereinthe controller is configured to command the primary on-coming clutch toan initial primary on-coming setpoint prior to entering closed loopcontrol, the initial primary on-coming setpoint determined based on themodel.
 38. The system as in claim 36, wherein the controller isconfigured to command the secondary off-going clutch to an initialsecondary off-going setpoint prior to entering closed loop control, theinitial secondary off-going setpoint determined based on the model. 39.The system as in claim 36, wherein the controller is configured tocommand the secondary on-coming clutch to an initial secondary on-comingsetpoint prior to entering closed loop control, the setpoint determinedbased on the model.
 40. The system as in claim 31, wherein a torqueconverter is connected between the input shaft and the power generationunit.